5-Sulfanyl­idene-2H,5H-1,3-dithiolo[4,5-d][1,3]dithiol-2-one

The title mol­ecule, C₄OS₅, is essentially planar, with an r.m.s. deviation of 0.032 (3) Å. All the C—S single bonds are shorter than the standard Csp³—S single-bond length, showing the π-conjugated nature of the molecule. In the crystal, molecules lie parallel to one another and pack in columns along the a axis. Short inter­molecular S...S contacts [3.314 (3), 3.482 (2) and 3.501 (2) Å] are observed between the columns. The angle between the two mol­ecular dipole moments in the unit cell is 39.3 (1)° and the macro-polarization vector is along the [1 0 − 1.41] direction. As a result of the high polarization and π-conjugation of the structure, the crystalline powder exhibits a second harmonic generating intensity, which is as strong as that of the urea standard powder crystals, when irradiated by a 1053 nm laser beam. The diffraction space of the crystal showed a nonmerohedral twinning.

Bis(4-amino­pyridinium) tetra­iodido­cad­mate monohydrate

The title compound, (C₅H₇N₂)₂[CdI₄]·H₂O, contains one [CdI₄]²⁻ anion, two prontonated 4-amino­pyridine mol­ecules and one water mol­ecule in the asymmetric unit. In the anion, the Cd^II atom is coordinated by four I atoms in a slightly distorted tetra­hedral geometry. The [CdI₄]²⁻ anion and the water mol­ecule are bis­ected by a crystallographic mirror plane perpendicular to the c-axis direction, with the Cd^II atom, two of the I atoms and the atoms of the water mol­ecule located on this plane. The crystal packing is stabilized by inter­molecular N—H...I, N—H...O and O—H...I hydrogen bonds and by π–π stacking inter­actions [centroid–centroid distance = 3.798 (3) Å) between pyridine rings, which build up a three-dimensional network.